Transcript for Police: Boston Suspect's NYC Plot Was Spur of the Moment

Times square. That is where we now learned the alleged boston bombers were headed, until their plot was thwarted, when their carjack victim made a daring escape. And we're going to hear more from him this morning. We will. Let's get right, now, to more on the big headline that just broke. As we told you, the younger suspect, moved overnight. Abc's brian ross is here with all of the latest details for us. Good morning, brian. Reporter: That's right, robin. His condition had improved enough to make his move possible. And his continued presence at a hospital where his victims were being treated was a serious irritant to those victims and their families. Under heavy security, u.S. Marshals quietly moved dzhokhar tsaranev to the president deven federal prison hospital. The move came as the new revelations about the brothers' plan to attack new york raised questions about their level of training. They made the decision to come to new york with their unexploded bombs on the spur of the moment. That's what the police commissioner says the fbi told him about the two accused terrorists. They discussed this while drivinound in a mercedes suv that they had hijacked after they shot and killed an m.I.T. Police officer in cambridge. Reporter: But the plan was foiled when they had to stop for gas in the stolen car. And one of the brothers went inside for snacks. The driver used the opportunity to escape and call the police. That eventually led to the shoot-out in watertown. Reporter: That shoot-out, captured in these still photos, involves a violent gun fight. And they used up some of the six unexploded bombs they had. They have explosives here at the scene. Explosives at the scene. Reporter: Some of what officials fear might have been used in times square. We don't know if we would have been able to stop the terrorists if they hthey arrived here from boston. Reporter: The accused bomber, came during an interrogation conducted before he was read his rights. And which republican congressman, peter king, says ended while fbi agents were still far from finished. My understanding was, the interrogation was going to last about 48 hours. It was ended by the judge after 16 hours. Reporter: The fbi says the talk of an attack on times square was just talk. And never an actual plot. Even so, if successful, security experts say the damage in this busy crossroads could have been a lot worse than what happened in boston. You could have one score or two scores of casualties and twice that number wounded. Reporter: The body of the dead tsaranev brother remains unclaimed at the boston medical examiner's office. And the father of the two boys in russia says he's trying to raise the money to buy a picket to come here and claim it. Josh? Thank you, brian.

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